Corrections in red.  Stylistic suggestions and variants in blue.

The Best Poem  [Capitalize the first, last, and all other words in a title, except articles, coordinating conjunctions, prepositions, the word "to" in infinitives, and the conjugated forms of the verb "to be.]

My favorite Russian poet is Yesenin, but my favorite poem wasn't written by him. This poem shows the most painful moment in all of Russian history: the Second World War. I recommend this poem to everyone, especially to non-Russians.
This poem is titled <em>I Was Killed Near Rzhev</em> (Я убит подо Ржевом), and was written by Tvardovsky. Excuse me, if I translated the title of the poem incorrectly. This poem is based on actual events/the true story.